Das Spektrum der verzögerten Fluoreszenz in Anthracen-und Naphthalin-Kristallen

1970 ◽  
Vol 25 (5) ◽  
pp. 657-664 ◽  
Author(s):  
K. W. Benz ◽  
W. Hacker ◽  
H. C. Wolf
Keyword(s):  
Temperature Dependence ◽  
High Purity ◽  
Trap Depth ◽  
Delayed Fluorescence ◽  
Mixed Crystals ◽  
Pure Crystal ◽  
Guest Molecules ◽  
Prompt Fluorescence ◽  
Broad Continuum

The spectra of delayed fluorescence of high purity anthracene and naphthalene crystals have been measured as a function of temperature. Below 50 °K they are very different from the spectra of prompt fluorescence. The spectra of delayed fluorescence are the superposition of three types of subspectra: different X-traps-spectra, a broad continuum, and the pure crystal spectrum. From the temperature dependence of the relative intensities of these spectra one can measure the trap depth. - It is shown that the delayed fluorescence is at least 100 times more sensitive against traps and guest molecules than the prompt fluorescence. This is demonstrated using naphthalene-anthracene mixed crystals.

Konzentrations-und Temperaturabhängigkeit der Sensibilisierten Verzögerten Fluoreszenz in Naphthalin/Anthracen-Mischkristallen / Sensitized Delayed Fluorescence in Naphthalene/Anthracene Mixed Crystals: Concentration and Temperature Dependence

1975 ◽  
Vol 30 (3) ◽  
pp. 277-286 ◽  
Author(s):  
H. Port ◽  
M. Bader ◽  
G. Weber ◽  
H. C. Wolf
Keyword(s):  
Energy Transfer ◽  
Temperature Dependence ◽  
Concentration Dependence ◽  
Energy Transport ◽  
Delayed Fluorescence ◽  
Mixed Crystals ◽  
Temperature Range ◽  
Host Molecules ◽  
Hopping Model ◽  
Triplet Excitons

The delayed fluorescence of naphthalene crystals doped with anthracene has been investigated for concentrations between 7 × 10-9 and 10-5mol/mol in the temperature range 4.2 -300 °K. The concentration dependence of both the quantum ratio of host and guest emission and of the lifetime shows the effectivity of energy transfer by triplet excitons. It can be described quantitatively within the statistical hopping model, which includes the probability for an exciton to visit the same host molecules repetitively before becoming trapped. This incoherent energy transport becomes faster as the temperature is lowered. The exciton hopping time decreases monotonically from tʜ = 2 × 10-10 sec at 300 °K to tʜ = 8 × 10-11 sec at 130 °K. Below 100 °K the delayed fluorescence is governed by competing trapping effects.

The electronic spectra of mixed crystals

1963 ◽  
Vol 271 (1345) ◽  
pp. 207-217 ◽  
Keyword(s):  
Intermolecular Interactions ◽  
Electronic Spectra ◽  
Mixed Crystal ◽  
Electronic States ◽  
Dipole Approximation ◽  
Mixed Crystals ◽  
Excited Electronic States ◽  
Guest Molecules ◽  
Rough Approximation ◽  
Crystal Properties

The excited electronic states of dilute mixed crystals are discussed in terms of the theory of intermolecular interactions in dipole-dipole approximation. Resonance interactions of the Davydov type, which are of the first importance in pure crystals, are absent. However, interactions between host and guest molecules are generally of com parable importance to second-order interactions in pure crystals, and lead to similar changes in absolute absorption intensities and polarization ratios. There is a substantial departure from oriented-gas behaviour, which can be regarded as only a rough approximation to mixed crystal properties.

Optical Spectroscopy of Mixed Metamagnetic FexCo1-xCl2 Crystals

1980 ◽  
Vol 35 (10) ◽  
pp. 1013-1019 ◽  
Author(s):  
Friedrich Seitz ◽  
Terence E. Wood ◽  
Peter Day
Keyword(s):  
Charge Transfer ◽  
Temperature Dependence ◽  
Single Crystals ◽  
Absorption Spectra ◽  
Optical Spectroscopy ◽  
Electronic Absorption ◽  
Electronic Absorption Spectra ◽  
Broad Band ◽  
Mixed Crystals ◽  
Magnetic Exchange

Abstract Electronic absorption spectra are reported for single crystals of composition FexCo1-xCl2 as a function of temperature from 300 K to 4 K. A broad band at 436 nm is assigned to Fe (II) → Co (II) charge transfer and the temperature dependence of its intensity is related to the magnetic exchange between the ions. The 2T1g(2H) excitation of Co (II) in the mixed crystals has an unusual temperature dependence which correlates with the Néel temperature.

Temperature Dependence of the Elastic Constants of Gallium

1975 ◽  
Vol 53 (6) ◽  
pp. 581-582 ◽  
Author(s):  
T. J. Langill ◽  
J. Trivisonno
Keyword(s):  
Single Crystal ◽  
Temperature Dependence ◽  
Elastic Constants ◽  
High Purity ◽  
Acoustic Waves ◽  
Ultrasonic Pulse ◽  
Pulse Echo

A modified ultrasonic pulse overlap technique was employed to measure the single crystal elastic constants of high purity gallium from 4.2 K to 190 K. The results are compared with data obtained by a technique which employed direct electromagnetic generation of acoustic waves as well as with earlier pulse echo measurements.

Deformation of guest molecules in the C60 based mixed crystals

1998 ◽  
Vol 16 (1) ◽  
pp. 31-34 ◽  
Author(s):  
K.T Antonova ◽  
M.K Marchewka ◽  
E Kowalska ◽  
P Byszewski
Keyword(s):  
Mixed Crystals ◽  
Guest Molecules

Delayed Fluorescence of Mixed Crystals

1965 ◽  
Vol 42 (10) ◽  
pp. 3720-3721 ◽  
Author(s):  
L. Azarraga ◽  
T. N. Misra ◽  
S. P. McGlynn
Keyword(s):  
Delayed Fluorescence ◽  
Mixed Crystals
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